Component suction head for electronic component mounting machines

ABSTRACT

An object of the present invention is to offer a component suction head for electronic component mounting machines which is capable of securely holding electronic components by suction and smoothly mounting them on printed wiring boards without dislocation. To achieve the objective, the component suction head of the present invention comprises the following. A suction nozzle unit 24 has a suction face 33 at the center of its tip, for holding electronic component 10, and a through hole 27 formed at its center which leads to the suction face 33. The back end of the through hole 27 is connected to a vacuum generator. An elastic ring 32 is fitted and fixed around the through hole 27 to the tip of the suction nozzle unit 24, slightly protruding from the suction face 33. An ejector pin 28, which can protrude from the suction face 33 for a specified length, forms an intake passage 38 from the tip to the through hole 27, and is fitted to the through hole 27 in sliding fashion. A spring means 31 supports the tip of the ejector pin 28 to protrude from the suction face 33.

FIELD OF THE INVENTION

The present invention relates to the field of electronic componentmounting machines which automatically mount a range of electroniccomponents on printed wiring boards and, more particularly, to componentsuction heads which pick up electronic components by suction formounting them on printed wiring boards.

BACKGROUND OF THE INVENTION

General configuration of electronic component mounting machines is shownin FIG. 3. A printed wiring board 3 is supplied on a transfer rail 2from the side of a mounting machine 1, and positioned at a specifiedmounting area. A suction head 8 picks up by suction a component set in aparts feeder 4 disposed at the front of the mounting machine 1,transfers the component over the printed wiring board 3, and mounts itat a specified position on the printed wiring board 3.

The suction head 8 of the prior art employs a suction nozzle unit 9 atits tip as shown in FIG. 4. The suction nozzle unit 9 has a suction face12 at the tip of its nozzle body 11 for holding an electronic component10. A concave portion 13 for suction is formed at the center of thesuction face 12, and is led to an inlet hole 14 perforated through thevertical direction along the nozzle body 11. A fitting groove 18 isdisposed at the outer edge of the tip of the nozzle body 11. An O-ring17 is fitted and fixed to the fitting groove 18, slightly protrudingfrom the suction face 12. The suction nozzle unit 9 is connected to avacuum generator (not illustrated) by means such as a hollow shaft.

For holding the electronic component 10 by suction, as shown in FIG. 4,the suction head 8 lowers and the suction face 12 of the suction nozzleunit 9 is pressed against the surface of the electronic component 10.The O-ring 17 deforms as illustrated by its own elasticity, and tightlycontacts the surface of the electronic component 10 to form an airtightseal around the suction face 12. Then, when the vacuum pressure in theconcave portion 13 for suction increases as the vacuum generator isoperated, the surface of the electronic component 10 sticks to thesuction face 12 and the O-ring 17. Here, the electronic component 10 issecurely held by preventing air leakage with the O-ring 17 and keeping aspecified vacuum pressure in the concave portion 13 for suction. Afterthe electronic component 10 is transferred to above the specifiedposition on the printed wiring board 3, the vacuum generator stopsvacuuming operation, allowing the surface of the electronic component 10to be released from the suction face 12 and the O-ring 17.

An advantage of the suction head 8 employing the above conventionalsuction nozzle unit 9, compared to existing suction nozzle units whichuse a diamond, is its reliable holding power by means of improvement ofthe vacuum rate for the electronic component 10 with the use of theO-ring 17. On the other hand, however, the O-ring 17 may not smoothlyseparate from the electronic component 10 when the vacuum is switchedoff at mounting the electronic component 10 on the printed wiring board3, due to its own viscosity, because the O-ring 17 is made of a materialsuch as rubber. In some cases, the electronic component 10 sticks to theO-ring 17 as the suction head 8 rises, and the component bounces orslightly moves on the printed wiring board 3. Therefore, the prior arthas a disadvantage in mounting the electronic component 10 accurately onthe printed wiring board 3, making it difficult to realize high densitymounting of electronic components 10.

DISCLOSURE OF THE INVENTION

An object of the present invention is to offer a component suction headfor electronic component mounting machines which can securely holdelectronic components and smoothly mount them on printed wiring boardswithout dislocation.

To achieve the object, the present invention relates to a componentsuction head for electronic component mounting machines for holdingelectronic components by suction and mounting them on boards whichcomprises the following. A suction nozzle unit has a suction face at itstip for holding electronic components. A through hole is perforated atthe center of the suction nozzle unit, and one end reaches the suctionface and the other end at the back is connected to a vacuum generator.An elastic ring is fitted and fixed around the through hole at the tipof the suction nozzle unit, slightly protruding from the suction face.An ejector pin is fitted in sliding fashion to the through hole and itstip can protrude from the suction face for a specified length. An intakepassage is formed from the tip of the ejector pin to the through hole. Aspring means supports the tip of the ejector pin to protrude from thesuction face.

Furthermore, an air inlet opening which leads to the intake passage isprovided at a tip of the ejector pin

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical section view of a part concerned of a componentsuction head of an exemplary embodiment of the present invention.

FIG. 2 is a vertical section view illustrating the process of picking upby suction and mounting electronic components using the componentsuction head of the present invention.

FIG. 3 is a perspective of an electronic component mounting machineapplicable to the present invention and component suction heads of theprior art.

FIG. 4 is a vertical section view of the conventional component suctionhead.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the present invention, when the suction face of a suction nozzle unitis pressed against the surface of an electronic component, theelectronic component presses an ejector pin back into the suction nozzleunit, against the support force of a spring means. Although the supportforce of the spring, which is equivalent to the restoring force, isapplied to the electronic component, air leakage between a through-holeand the electronic component can be prevented because the vacuum suctionpower generated by operating a vacuum generator is applied to theelectronic component through the through hole of the suction nozzle andthe intake of the ejector pin. Air leakage is also prevented by anelastic ring which elastically deforms to tightly contact the surface ofthe electronic component. Thus, the electronic component is securelysucked and held by the suction face and elastic ring of the suctionnozzle unit.

Then, when the suction head rises, after the electronic component ismounted on a board and the vacuum generator stops, the ejector pinprotrudes from the suction face due to the restoring force of the springmeans and presses the surface of the electronic component. This enablesthe elastic ring to smoothly release the electronic component, andthereby assuring accurate mounting of the electronic component on theprinted wiring board.

An exemplary embodiment of the present invention is explained below withreference to drawings.

FIG. 1 is a vertical section view of a part concerned illustrating acomponent suction head 20 of an exemplary embodiment of the presentinvention which is mountable on electronic component mounting machinesshown in FIG. 3. The component suction head 20 is attached to a hollowshaft 21 connected to a vacuum generator (not illustrated) and comprisesthe following. A hollow shaft 22 comprises a small-diameter holding hole30 and a large-diameter holding hole 23 at its core. A suction nozzleunit 24 is disposed in sliding fashion inside the large-diameter holdinghole 23 of the hollow shaft 22. An ejector pin 28 is fitted in slidingfashion into the through hole 27 of the suction nozzle unit 24. A holder29 is disposed on top of the ejector pin 28 and screwed to the top endof the suction nozzle unit 24, and its upper part is held in slidingfashion with the small-diameter holding hole 30 of the hollow shaft 21.A spring means 31 consists of a coil spring and is provided between theholder 29 and the ejector pin 28 for supporting downward movement of theejector pin 28. An elastic ring 32 consists of an O-ring and is fittedand fixed around the bottom end of the suction nozzle unit 24.

The lower end face of the suction nozzle unit 24 forms a suction face 33which contacts an electronic component 10 in the same way as inconventional nozzle units. A concave portion 34 for suction which leadsto the through-hole 27 is provided at the center of the suction face 33.The elastic ring 32 is fitted and fixed to a fitting groove 37 of thesuction nozzle unit 24, slightly protruding from the suction face 33.The ejector pin 28 comprises an inlet hole (intake) 38 which is athrough hole along the shaft. An air inlet opening 39 is provided at thebottom end of the ejector pin 28 by engraving the bottom end in a Ushape so that the inlet hole 38 is led to the outer air by the air inletopening 39 from the side of the tip face.

The ejector pin 28 has a catch rib 40 projecting from its top part. Thebottom tip of the ejector pin 28 protrudes from the suction face 33 fora specified length by the support force of the elastic ring 32 when thecatch rib 40 is pressed against a catch step 41 of the suction nozzleunit 24. An inlet hole 42 which is a through hole along the shaft isprovided on the holder 29, and accordingly, a vacuum exhaust passage isformed through the inlet hole 38 of the ejector pin 28, the through hole27 of the suction nozzle unit 24, the inlet hole 42, the small-diameterholding hole 30, and the hollow shaft 21 to the vacuum generator.

This exemplary embodiment is capable of balancing the difference inthickness of the electronic component 10. At one side of the suctionnozzle unit 24 which is disposed in sliding fashion in the hollow shaft22, a guide groove 43 is provided in the sliding direction of thesuction nozzle unit 24, and a tip of a guide pin 44, which is attachedthrough the hollow shaft, fits in sliding fashion into the guide groove43. Under normal conditions, a coil spring 47 provided between thesuction nozzle unit 24 and the hollow shaft 22 supports the suctionnozzle unit 24 downward. In this state, the suction nozzle unit 24 isheld at the lower limit position where the guide pin 44 contacts theupper end of the guide groove 43. The range of up/down movement of thesuction nozzle unit 24 is restricted by the guide pin 44 and the guidegroove 43, and the suction nozzle unit 24 can be drawn back in thehollow shaft 22 from the above lower limit position to the upper limitposition where the guide pin 44 contacts the lower end of the guidegroove 43.

The operation of the component suction head 20 is explained withreference to FIG. 2.

As shown in FIG. 2 (a), when the suction head 20 does not contact theelectronic component 10 in the normal state, the ejector pin 28 isforced to protrude from the suction face 33 by the support force of thespring means 31 for a specified length, and the suction nozzle unit 24is held at the lower limit position. Under these conditions, thecomponent suction head 20, as marked by the arrow in FIG. (a), lowerstowards the surface of the electronic component 10 in a parts feeder 4,and the suction face 33 is pressed against the surface (top face) of theelectronic component 10, as shown in FIG. 2 (b).

When the suction face 33 of the suction nozzle unit 24 is pressedagainst the electronic component 10, the tip of the ejector pin 28contacts and is subsequently pressed back by the electronic component10, and the ejector pin 28 is drawn into the suction nozzle unit 24,against the support force of the spring 31, until the tip becomes levelwith the suction face 33 as shown in FIG. 2 (b). The suction nozzle unit24 is drawn into the hollow shaft 22, as the coil spring 47 iscompressed by the electronic component 10, in order to balance thedifference in the thickness of the electronic component 10.

At this point, the vacuum generator operates and increases the degree ofvacuum in the concave portion 34 for suction through the aforementionedvacuum exhaust passage and the air inlet opening 39. The suction forcelifts the electronic component 10 toward the suction face 33 and theelastic ring 32. Here, the restoring force of the compressed spring 31exits when the ejector pin 28 is drawn into the suction nozzle unit 24,and this force, the support force equivalent to the restoring force, isapplied to the electronic component 10. In other words, a force isapplied which acts to release the electronic component 10 away from thesuction nozzle unit 24. However, the suction face 33 of as the suctionnozzle unit 24 and the elastic ring 32 are capable of securely holdingthe electronic component 10 by suction because the suction power of thevacuum generator is applied to the electronic component 10 and theelastic ring 32 deforms to tightly contact with the surface of theelectronic component 10, thus forms airtight seal around the concaveportion 34 for suction to prevent air leakage.

Next, after the component suction head 20 rises, holding the electroniccomponent 10 by suction, it moves over the specified mounting positionon a printed wiring board 3 and lowers to mount the electronic component10 on the printed wiring board 3 as shown in FIG. 2 (c). When thecomponent suction head 20 rises after the vacuum generator switches off,the ejector pin 28 protrudes downward for the specified length from thesuction face 33 by the restoring force of the spring means 31, andpresses the surface of the electronic component 10 after it is releasedfrom the suction power as shown in FIG. (d). Since the ejector pin 28forcibly releases the electronic component 10, the elastic ring 32smoothly and effortlessly separates from the electronic component 10.Consequently, the electronic component 10 can be mounted on the printedwiring board 3 without any dislocation.

In the above exemplary embodiment, the inlet hole 38 is provided in theejector pin 28 along the shaft as an air intake for vacuuming air withthe vacuum generator. Such air intake could be provided between theejector pin 28 and the suction nozzle unit 24 by creating a groove in avertical direction on either the ejector pin or the suction nozzle unit24. Also the exemplary embodiment provides the air inlet opening 39 byengraving the bottom end of the ejector pin 28 in a U shape. Suchopening could also be made at the side of the ejector pin 28 which leadsto the inlet hole 38. Furthermore, if the air intake is provided betweenthe ejector pin 28 and the suction nozzle unit 24 as mentioned above,there is no need to provide a separate air inlet opening. In otherwords, as long as the inlet hole 38 is not blocked by the electroniccomponent 10 when the flat tip of the ejector pin 28 contacts thesurface of the electronic component 10, any structure is embraced in thescope of the present invention.

Industrial Applicability

As described above, the present invention is capable to securely holdelectronic components by suction power of the vacuum generator appliedto the electronic component through the through hole of the suctionnozzle unit and the intake of the ejector pin, and by the elastic ringwhich deforms and tightly contacts the surface of the electroniccomponent to prevent air leakage. At mounting the electronic component,the ejector pin protrudes from the suction face by the restoring forceof the spring and presses the surface of the electronic component toforcibly release the electronic component from the elastic ring. Thus,the present invention is capable of mounting the electronic component onthe printed wiring board without any dislocation.

What is claimed is:
 1. A component suction head for electronic componentmounting machines for holding electronic components by suction andmounting said components on boards comprising:a suction nozzle unit,which has a suction face at a tip of said suction nozzle unit forholding electronic components, and a through hole in a center of thesuction nozzle unit, one end of said through hole located at the suctionface and another end of said through hole located at an end of saidsuction nozzle unit opposite to said tip for communication to a vacuumgenerator; an elastic ring fitted and fixed around said suction nozzleunit at the tip of the suction nozzle unit, said elastic ring slightlyprotruding from said suction face; an ejector pin slidably fitted insaid through hole, said ejector pin having an end portion and an airinlet opening formed from a tip of said end portion of the ejector pinto said through hole; and a spring, biasing the ejector pin, so thatsaid end portion of said ejector pin protrudes from said suction face bya specified length in the absence of a vacuum from said vacuumgenerator, wherein when said suction face holds an electronic componentat an upper surface thereof and said vacuum generator provides thevacuum, said ejector pin is drawn into said through hole compressingsaid spring and said end portion of said ejector pin does not protrudefrom said suction face, and when said vacuum generator stops providingthe vacuum while said suction face holds said electronic component, arestoring force of the compressed spring pushes the ejector pin toprotrude an end portion from said suction face and press said uppersurface of the electronic component.
 2. The component suction head forelectronic component mounting machines as defined in claim 1,wherein anair inlet opening, which leads to said through hole is provided at thetip of said end portion of said ejector pin.
 3. A component suction headfor electronic component mounting machines for holding electroniccomponents by suction and mounting said components on boardscomprising:a suction nozzle unit, which has a suction face at a tip ofsaid suction nozzle unit for holding electronic components, and athrough hole in a center of the suction nozzle unit, one end of saidthrough hole located at the suction face and another end of said throughhole located at an end of said suction nozzle unit opposite to said tipfor communication to a vacuum generator; an elastic ring fitted andfixed around said suction nozzle unit at the tip of the suction nozzleunit, said elastic ring slightly protruding from said suction face; anejector pin slidably fitted in said through hole, said ejector pinhaving an end portion and an air inlet opening formed from a tip of saidend portion of the ejector pin to said through hole; and a spring,biasing the ejector pin, so that said end portion of said ejector pinprotrudes from said suction face during mounting, wherein when saidsuction face holds an electronic component at an upper surface thereofand said vacuum generator provides a vacuum, said ejector pin is drawninto said through hole compressing said spring and said end portion ofsaid ejector pin does not protrude from said suction face, and when saidvacuum generator stops providing the vacuum while said suction faceholds said electronic component, a restoring force of the compressedspring pushes the ejector pin to protrude said end portion from saidsuction face and press said upper surface of the electronic component.4. A method of mounting an electronic component on a board comprisingthe steps of:sucking an electronic component with a suction unit forholding said electronic component; transferring said electroniccomponent to a specified mounting position on a board; stopping sucking;and pressing said electronic component after sucking stops with an endportion of an ejector pin that is slidably fitted in a through hole insaid suction unit, to release said electronic component from saidsuction unit.